1. Field of the Invention
The present invention relates to a method of supporting media independent handover, and more particularly, to a method of supporting media independent handover with a resource management function in a mobile communication system.
2. Discussion of the Related Art
IEEE802.21 is in the International standardization stage for media independent handover (MIH) between heterogeneous networks, and is to provide seamless handover and service continuity between heterogeneous networks in order to improve a user's convenience for a mobile terminal. The IEEE802.21 defines basic requirements such as an MIH function, an event service (ES), a command service (CS), and an information service (IS). The mobile terminal can also be referred to as a mobile station, a terminal, a mobile subscriber station, and a like. Further, a base station can also be referred to as a node, point of attachment, a network, a base terminal, and a like.
The mobile terminal is a multimode node that supports one or more interface types, wherein the interface may be one of the following types:                Wire-line type such as 802.3 based Ethernet;        IEEE802.XX based wireless interface;        802.11        802.15        802.16        Interface prescribed by a cellular standardization mechanism such as 3GPP and 3GPP2.        
As shown in FIG. 1, a multimode mobile terminal has a media access control layer and a physical layer of each mode, and an MIH function is a logic entity and can freely be arranged while implementing interface through each layer and a service access point (SAP) within a protocol stack.
Media independent handover (MIH) should be defined between 802 based interfaces or between the 802 based interfaces and non-802 based interfaces 3GPP and 3GPP2 mentioned above. A mobility management protocol of an upper layer such as a mobile IP and a session initiation protocol (SIP) should be supported for handover and a seamless service.
Hereinafter, a related art handover between heterogeneous networks will be described.
First, the MIH function will be described. The IEEE802.21 standard is to assist various handover methods to be easily operated, wherein the handover methods can be classified into break before make and make before break. The media independent handover function (MIHF) provides an asymmetric service such as a media independent event service (MIES) and a symmetric service such as a media independent command service (MICS) to upper layers and lower layers through a service access point (SAP). The MIH technique includes three MIHF services and a media independent handover protocol. The three MIHF services include a media independent event service (MIES), a media independent command service (MICS), and a media independent information service (MIIS).
Hereinafter, the event services will be described. The media independent event service is information forwarded from a link layer to upper layers, wherein the upper layers can receive the information through a registration procedure. In this case, in order to assist handover by predicting handover, the upper layers including the mobility management protocol are required to receive link layer information as to that handover will occur soon or handover has been just implemented. The media independent event service can be classified into a link event terminating at the MIHF from an entity that has generated an event in lower layers (second layer and below) and an MIH event forwarded to upper layers (third layer and above) registered by the MIHF. The link event and the MIH event can be classified into two types depending on areas to which they are forwarded. If the events are generated from an event source within a local stack and forwarded from the event source to a local MIHF or from the MIHF to the upper layers, they are referred to as local events. If the events are generated from a remote event source and forwarded from the remote event source to a remote MIHF and then from the remote MIHF to the local MIHF, these events are referred to as remote events.
FIG. 2 illustrates a structure of a local event model and an MIH event model. The MIH events are forwarded from the MIH to a higher management entity or an upper layer, and correspond to event triggers of the related art. The link event is forwarded from the lower layer (MAC or physical layer) to the MIH, and primitives are used as the link event, wherein the primitives are used in each interface MAC or physical layer.
FIG. 3 illustrates a structure of a remote link event model. If an event is generated from a lower layer in a local stack to the MIH in the same local stack, the MIH forwards the event to the MIH of a remote stack. Also, the event may be generated from the lower layer of the remote stack to the MIH of the remote stack, whereby the MIH of the local stack may receive a trigger.
FIG, 4 illustrates a structure of a remote MIH event model, Referring to FIG. 4, the MIH in the local stack generates a remote MIH event and forwards the generated remote MIH event to the other MIH in the remote stack. The other MIH forwards the remote MIH event to an upper management entity or an upper layer in its stack. Also, the event may be generated from the MIH in the remote stack to the MIH in the local stack, whereby the upper layer of the local stack may receive a trigger.
Hereinafter, the command service will be described. The media independent command service corresponds to commands sent from the upper layers (third layer and above) to the lower layers (second layer and below) to allow the upper layers and other MIH users to determine the link status and adjust an optimized operation of a multimode device. Similarly to the media independent event services, the media independent command service is classified into a link command and an MIH command. The link command and the MIH command are classified into a local command and a remote command depending on areas to which they are forwarded. A local MIH command is generated from the upper layers and then forwarded to the MIHF (for example, from the mobility management protocol of the upper layer to the MIHF or from a policy engine to the MIHF). Local link command languages are generated from the MIHF to adjust lower layer entities and then forwarded to the lower layers (for example, from the MIHF to the media access control layer or from the MIHF to the physical layer). A remote MIH command is generated from the upper layers and forwarded to a remote peer stack, and a remote link command is generated from the MIHF and transmitted to the lower layers of the remote peer stack.
FIG. 5 illustrates a structure of an MIH command model and a link command model. The MIH command is generated from the upper management entity or the upper layer and then forwarded to the MIH, and is to command the MIH to take some action. The link command is generated from the MIH and then forwarded to the lower layer, and is to command the lower layer to take some action.
FIG. 6 illustrates a structure of a remote MIH command model. The remote MIH command is generated from the upper management entity or the upper layer in the local stack and then forwarded to the MIH. The MIH forwards the remote MIH command to the other MIH in the remote stack. Also, the remote MIH command may be generated from the upper layer of the remote stack to the MIH of the remote stack, whereby the MIH of the local stack may receive the command.
FIG. 7 illustrates a structure of a remote link command model. The MIH in the local stack generates the remote link command and forwards the generated command to the other MIH in the remote stack. The other MIH forwards the command to the lower layer in the remote stack. Also, the command may be generated from the MIH in the remote stack to the MIH in the local stack, whereby the lower layer of the local stack may receive the command.
Hereinafter, the information service will be described. The media independent information service is for homogeneous or heterogeneous networks in a local area. The MIHF of the networks as well as the MIHF of the mobile terminal can detect and acquire the media independent information service. The media independent information service includes various kinds of information elements required to determine intelligent handover.
The aforementioned related media independent handover has the following problems.
In the related art, the procedure of handover from an old point of attachment to a new point of attachment is defined for the media independent handover. However, a problem occurs in that it takes a long time to resume communication when new communication is resumed due to failure of handover for the new point of attachment, or when the link with the old point of attachment is preferred as a signal with the old point of attachment is desirably resumed within a short time after handover from the boundary between two points of attachments to a new point of attachment is determined and the link with the new point of attachment is set up. Another problem occurs in that the multimode mobile terminal fails to implement a proper operation of data forwarded thereto after handover as data buffering from the old point of attachment to the new point of attachment is not forwarded to the mobile terminal.